I was having a similair problem. I received a "Whoops! Your session has expired" error everytime a customer went to checkout. Additionally, the Zen Cart would revert to showing "Log In" instead of "Log Off" immediately after Loggin in. Also, I was receiving an "About:Blank" Page IN BETWEEN every page after logging in. (This WIPED out the session.
Here was MY solution:
1) Went to phpMyAdmin and opened the zen_sessions SQL File and then did a "Repair Table" command from the Table Maintenance area under the Operations area.
FINALLY, after days of not having orders..., The site now works again!
Hope this helps someone.
Daniel Osko
Bookmarks